Air-pressure gauge



March 24, 1931. V A. E. cARLlss 1,797,324

AIR PRESSURE GAUGE Filed April 25, 1928 2 sheetssheet 1' INVENTOR.

A TTORNEYX.

4/er/ Car/G5 March 2-4, 1931. A. E. CARLISS 1,797,324

AIR PRESSURE GAUGE Filed April 25, 1928 2 Sheets-Sheet 2 INVENTOR.

BY 1:1 a

A TTORNEYj.

4/ber/ farw Patented Mar. 24, 1931 nmsnnrncnntiss, oFrLoRALrARKuEw yoax,'as m;maro Admi Ara urrtmucn'i nnt-rnnssuun GAUGE Application filedApril 25,

Thisjinvention' relates to the art of air pressure gauges, andparticularly to that type of gauge wherein what 18 known as a Bourdontube zis employed. It has for its object, the supplying oi' means bywhich the operationfofsuch Bourdon tube will be mademore certain andeificient.

\Vhat is known as a Bourdon tube as emi tendency to resume its normalform.

As previously stated, such t beis'anchored to a fixed support atone endwherethe air l underpressureg is] introduced, and the S oppo'sitefliendof said tube is free and unre-l. strained-to'move from its normalpositionto an abnormal position, dependent, .upon the degree of airpressuretintroduced into the, tube. gForthe-purpose of determinmg the 30degreegof air pressure,;-a pivotally' mounted index hand is caused to-move over Q the face of ,a scaleby means oiia link interposed be-,tweentthefreeend of thetube and said index "hand so that When the Vfreeend of. the tube: V I p ,trating the operation of a'Bourdon tube ismoved bythe air pressure introduced into the tube, thehand is caused torespondto such imovement. Given that-the degree of airv pressureintroduced into the tube is known, it is possible to adjust ,the Indexhandlln as degree of pressureintroduced into the tube.

possible to, manufacture such' tubes vvith a operateinexactlythe sameWay under vsimi riideg es. ot-ane suw C n q nt y free end of said tubeWlnch, as previously the tube at the .point of'suchlanchorage or, base,and such air pressure operates-more or lessito lenlarge the arc of thenormal form ofsuch a tube,.-and causes the, same to tend to approach astraightline With the re lease of such air pressure, saidtube has at hasbeen 3 possible heretofore.

sooiationnwith a scale so as, to indicate the.

192a "Serial No. 272,625;

statedis linlred to the lindexfhand;

performs its function inanuncertain and variable manner, hence giving areading wh ch 1s correspondingly variable according;

characteristics of such tube.

to -tlie variation in the; flexibility or other:

This invention relates partlcularly to means whereby a variation in themovement of the freeendofthe said Bourdontube maybe re}, i duced to aminimum; This is accomplishedby provldlng, means whereby, the movementof the free end of theftllb Willbe confined or;- limited .to operateWithin aprede'termined are l of; a circle. Under Qsuchfconditions it ispossible tozproduce a gauge, that will, operate with far. greateraccuracyand certainty than;

The invention is illustrated in the accom panymg drawings, the severalparts being indicated by "numerals, like; numera1s.reer'- .ring to likeparts. i i

F re liearla i w/ i i egw ei the: top and- ,scale hav ng been removedto.

show theoperativeparts; g .4

Figure. la is aldetail, partlyin sectioin, Figure is the same as F igure1,' i vith'the exception that the link hereafterfto be'describedispivoted at a center more'remote from the free en 1 ofthe tube thanthat shown in Figurel; k v

under the conditions established in this case.

Figure 5 isaldiagrammaticyiew illustrat ing theoperationof a,Bourdonitube of the 7 type illustrated in FigureS.

1 is acasing adapted to eucl ose the order support suitably mountedWithinsaidcasing. a 3 isa conduit shown ,in do tted lines through.the-base of said. central support; 4 is a tube connectedwith saidconduit, (adapted for the i atingimechanism"of,algau'ger 2is, acentralsupply ofairunder pressure; I Q5fis a Bourdon tubeanchored at 6to-said.central'supportl and in communicatlon withsa d condu 1tj3,

7 indicates the free end lof tlie Bourdontub.

8 is a'link pivotally mounted at one end 0h Figure 3. is aplan viewaofagauge of, conthe central support 2 at 9, and the other end of said link8 is pivotally secured at 10 to the free end 7 of the Bourdon tube. 11is an index hand pivotally mounted on the support 2 at 12. 13 is a linksecured to the free end of the Bourdon tube 7 at 10, said link beingprovided with a hook 14 adapted to engage the index-hand 11 to move thesame over the face of a dial not shown. When said tube is operated underair pressure, it.

causes said index hand to move to the posi tion 15 and remain in thatpositionto give opportunity for a reading, as indicated by the hand 11and the scale over which it moves. When the air pressure is relieved,thelink 13 falls back to its normal position without affecting the positionof the index hand. 16

case is pivotally mounted 'at. 20. It will be obvious that the curvatureof the arcs16 and 21 will depend on the position of the center, of thecircle of which said arcs are part with reference to the position of thefree end of .the tube. that is, the longerthe radius, the

flatter the arc.

Figure 3, as previously statedis a plan view of a gauge employing aBourdon tube of the conventional type. The operation of such a tubeunder varying conditions of air' pressure is exhibited diagrammaticallyin Figure 5 wherein the tube in its normal position is indicated bv asolid line as 5. and the position ofthe tube under varying degrees ofpressure is exhibited in broken lines designated generally as 26.2611.and 267). be noted that under the said varying degrees of air pressure,the centers of the circles produced under such'varving conditions of airpressure vary in position as 24, 24/1. 247). and 24:0, and in likemanner the position of the free end of the tube varies. as indicated at10, 10a, 10?) and 100. It will also be noted thatthe curvature of a linedrawn through the free ends of the tube as diagrammaticallv exhibitedtakes the form as indicated at 25, and it will be observed that thisline 25 does not take the formot the arc of a circle as do the arcsindicated as 16 and 21. Indeedit may be said that under the varyingconditions It will ditions heretofore described, where the movement ofthe free: end of the tube is limited by the link 8 01'19. It will beobserved in this diagram that the centers 27, 27a, 27b,

270 and 27dall fall within a horizontal plane and that such centers willbe invariable. It will also be noted that the are 16 is definitelyrelated to the central pivotal point 9 so that the said are 16 is alwaysthe same, by reason of the fact that the free end of the tube ispivotally connected with the link 8, and that this link is pivoted at 9.The movement of the said free end of said tube is therefore positivelyconfined to a movement within the are 16.

The operation of the device is as follows: Air under pressure, beingintroduced into the tube, causes the same to expand in a mannerheretofore explained. By reason of the fact that the link 8 is pivotallyconnected between the pivotal point 9 and the free end of the tube, itis impossible for the free end of the tube to move otherwise than in theline of the are 16, or in the-line of the are 21, as shown in Figure 2.This condition having been established, it is found that a desirabledegree of accuracy can be obtained in establishing the relation betweenthe movement of the index hand and a predetermined scale.

In practice, the tube is subjected to, say, 60

degrees of pressure, thus causing the index hand to move to a definiteposition. This 60 degrees of pressure may then be indicated on thescale, and so in like manner greater degrees of pressure may beintroduced into the tube, and by noting the movement of the index hand,the proper scale may be established, from which accurate readings may betaken. It is found by experiencethat the limitation of the movement ofthe free end of the tube within a prescribed and predetermined arc lendsitself to a more accurate operation of the mechanism, and to a highdegree compensates for the irregularities incident to the constructionof the tube, which more or less affects itsfiexibility, that is to say,when the free end of the tube is caused definitely to move'in aprescribed arc, there is a definite and permanent basis from whichto'calculate and compute the movement of the index hand underdifferentdegrees of air pressure.

While this has been described as useful in connection with determiningair pressure, p

the description herein designates particularly a gauge wherein it isdesirable to measure the I pressure and leave the hand in a fixedposition after the pressure is withdrawn, it will also be understoodthat it is applicable to that class Y of gauges wherein it is desirableto have the index'hand move backward and forwardaccording to theoperation of the free end of the Bourdon tube. In the latter case thefree end of the Bourdon tube will be definitely linked v to the indexhand,'thus indicating the rise and fall of pressure as the same occurs.All of these modifications are intended to be within the scope of thisinvention.

Claim:

' In an air pressure gauge of the Bourdon type, a Bourdon tube formed inan approximate circle and anchored at one end to a suitable support, theother end being free for 2Q movement, a link pivotally connected at oneend to said free end of said tube and also pivotally connected at theopposite end of said link at a fixed point which is the center of aprescribed circle of sufiicient dimension to embrace and include thecircle in which the Bourdon tube is formed, thus limiting the movementof said free end of said tube to a movement in the arc of saidprescribed circle, means secured to the free end of said tube to impartmovement of the free end of said tube to an index harid adapted tobeassociated with a suitable sca e.

I Signed by me at New York, N.'Y., this 24th a: day of April, 1928.

- I ALBERT E. CARLISS.

